1. Field of the Invention
The present invention relates to a chemiluminescent composition producing white light, and more particularly to an oxalate chemiluminescent composition capable of stably emitting brighter and purer white light even at low temperature.
2. Description of the Related Art
A general oxalate chemiluminescent composition comprises an oxalate solution and an activator solution wherein the oxalate solution includes an oxalate compound, a fluorescer and a solvent, and the activator solution includes hydrogen peroxide, a solvent and a catalyst. These components of the chemiluminescent composition are mixed in predetermined ratios to cause chemiluminescence. It is well established that favorable chemical/physical interactions are essential between the components for effective chemiluminescence, and also that the emitting light depends on the fluorescer.
Chemiluminescence in the oxalate chemiluminescent composition can be understood by a series of continuous multi-step chemical reactions. In the first stage, hydrogen peroxide and oxalate undergo reactions in an ester solvent, aided by a salicylate salt, producing an organic intermediate in an excited state. In the second stage, an excited fluorescer is produced through energy exchange between the excited organic intermediate and a fluorescer in a ground state. In the third stage, a ground state fluorescer is formed from the excited fluorescer by emitting light at the expense of extra energy [J. Amer. Chem. Soc. 89(25), 6515–6522 (1967); and Aust. J. Chem. 34, 1701–1717 (1982)].
Since the color of the light emitting from the oxalate chemiluminescent composition depends on the fluorescer, continuous efforts to develop a new fluorescer have been carried out up to present. But successful reports of a fluorescer which can be applied for practical purposes are rare in the literature. One of the primary reasons is that, as stated previously, interactions between the excited organic intermediate and the fluorescer in a ground state cannot be applied equally to all fluorescers in the oxalate chemiluminescence. Another reason is the requirement of the fluorescer to be chemically inert towards an oxidant such as hydrogen peroxide, an essential component in the oxalate chemiluminescence. If not, chemiluminescence time is shortened, thereby causing applications to commercial purposes to be difficult where long duration is required.
Anthracene derivatives are used as fluorescers for visible light such as blue, green, yellow-green and yellow light, as are seen in most commercial chemiluminescent products. Whereas perylenedicarboximide derivatives and pentacenes are used as fluorescers for red chemiluminescence.
Considering various applications including military purposes where it is crucial to discern obviously colored objects and to read figures and maps in the dark, the importance of developing white light can be easily understood. White light in principle can be produced by overlapping red, green, and blue, the essential three basic primary colors of light. But, up to present, there have been only a few reports on the production of white light utilizing chemiluminescence in spite of the extensive efforts by many researchers. One of the primary reasons is obviously due to the different chemical stabilities of each fluorescer producing the three basic primary colors, thereby causing inconsistency in the emitting color depending on the duration time.
Previous reports on the production of white light are described in U.S. Pat. Nos. 4,717,511 and 4,678,608, which teach that white light is produced from a composition comprising an anthracene-based fluorescer producing blue or green light and an N,N′-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylenedicarboximide represented by Formula 1 below:

wherein R is a t-butyl group.
But, in addition to the compound N,N′-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylenedicarboximide of Formula 1, most perylene compounds currently used as chemiluminescent dyes have negligible solubilities in organic solvents, including a compound represented by Formula 2 below:

wherein R is an alkyl or aryl group.
Solubilities in 100 mL of chloroform at 25° C. and synthetic yields according to various substituents of the compound of Formula 2 are shown in Table 1 below.
TABLE 1RSolubility (mg)Yield (%)Hexyl2376Dodecyl8.578Octadodecyl1.838Aryl3.242Cyclopropyl6.622Cyclobutyl8084Cyclopentyl8958Cyclohexyl6144Cycloheptyl1988Cycloctyl2.753Cyclononyl9.866Cyclodecyl9.840Cycloundecyl6550Cyclododecyl14045Cylclotridecyl1540Cyclotetradecyl150043Cyclopentadecyl330291-Ethylpropyl0.49461-Propylbutyl0.41371-Butylpentyl3.8421-Penylhexyl81261-Hexylheptyl78041
As shown in Table 1, the perylene compounds of Formula 2 show low solubilities in the organic solvent, except for the case where the substituent is a cyclotetradecyl group, as well as low synthetic yields.
Since the compound of Formula 2 shows a very low solubility in an organic solvent, it is precipitated at low temperature when it is used as a fluorescer. In particular, when the compound of Formula 2 is combined with other fluorescers, it exhibits a very low light intensity. Hence, the use of the compound of Formula 2 for chemiluminescence has a problem of difficult production of brighter and purer white light.
In conclusion, it is very important to select a fluorescer which shows higher solubility in organic solvents and increases light intensity due to good fluorescence in order to stably emit brighter and purer white light at low temperature. Based on this importance, the present inventor has extensively conducted research through the years with the aim of developing an oxalate chemiluminescent composition capable of producing white light, and as a result, accomplished the present invention.